Propellers are the most common source of propulsion for boats, ships, etc., and typically include a central hub with blades in the form of helicoidal surfaces that are attached to and extend outwardly from the hub. The propeller is commonly attached to a shaft that is either directly or indirectly attached to a motor, the motor operable to drive or rotate the shaft. Upon rotation of the shaft, and thus rotation of the propeller, the blades act to “screw” through the water and impart momentum to a fluid, e.g. water, in which the propeller is located and thereby apply a force to act on the boat, ship and the like. A propeller that turns clockwise to produce forward thrust when viewed from the aft is known as a right-handed propeller and one that turns counterclockwise a left-handed propeller.
Rotation of the propeller can also produce a low pressure region formed by fluidic velocity of circumferential flows and the low pressure region can form a vapor cavity known as a hub vortex. The hub vortex can cause a reduction in shaft thrust and an overall decrease in efficiency of a boat or ship propulsion system. While efforts have been made to reduce the hub vortex produced by a given propeller, such efforts have resulted in complex and costly additions to the ship propeller. For example, a propeller boss cap with fins (PBCF) is a boss cap that is attached to a hub or “boss” of a ship propeller and has the same number of fins as the blades of the propeller. The PBCF rotates with the propeller and the fins rectify water flow around the propeller boss to reduce and/or eliminate the hub vortex. As such, an improved propeller that reduces hub vortex without significantly increasing the complexity and cost of the overall propulsion system would be desirable.